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Plants have evolved mechanisms to avoid and repair UV radiation damage; it is not surprising that photomorphogenic responses to UV-B and UV-C are often assumed to be adaptations to harmful radiation. Free radicals generated by UV are likely to be involved in the induction of antioxidant defence system. In this study plants were grown for 5 weeks in controlled conditions. Plants were grown in vermiculite medium before applying the UV treatments, and irrigated daily by Hoagland solution for 5 weeks. After 5 weeks, plants were exposed to UV-A (320-390 nm), UV-B (312 nm), and UV-C (254 nm) irradiation with a density of 6.1 (Wm-2), 5.8 (Wm-2) and 5.7 (Wm-2) for 2 weeks. Each plant was exposed to UV in their light period for 27 min per day for 14 days. In each experiment 4 replicates were used. Data were analyzed using SPSS software, and averages were compared by Duncan's test. Activity of antioxidant enzymes could be found in the plant antioxidant defence system. The activity of antioxidant enzymes (namely, peroxidase, polyphenol oxidase, ascorbate peroxidase, catalase, and glutathione reductase) enhanced in leaves and roots of pepper plants in response to UV-B and UV-C radiation. The increase in the activity of antioxidant enzymes could minimise the effects of ultraviolet radiation. UV treatments induced significant increase in ascorbic acid in leaf and root of exposed plants. The present study was conducted to determine the role of antioxidant defence mechanism in UV-A, UV-B and UV-C treated plants of Capsicum annuum L. [ABSTRACT FROM AUTHOR]

Although ultraviolet radiation is potentially harmful, it is an important component of terrestrial radiation to which plants have been exposed since invading land. Since then, plants have evolved mechanisms to avoid and repair UV radiation damage. Therefore, it is not surprising that photomorphogenic responses to UV-B and UV-C are often assumed to be adaptations to harmful radiation. Most of the compounds accumulated are directly involved in UV-B and UV-C protection: they are either efficient in filtering excess radiation or in scavenging radicals. In this study plants were grown for 5 weeks in controlled environment room. The plants were grown in vermiculite medium using pots. Before UV treatments, plants were irrigated with nutrient solution (Hoagland solution) for 5 weeks. Then plants were exposed to UV-A (320-390 nm), UV-B (312 nm) and UV-C (254 nm) irradiation with a density of 6.1 (Wm-2), 5.8 (Wm-2) and 5.7 (Wm-2) for 2 weeks. Plants were treated with UV in their light period for 27 min per day for 14 days. The influence of UV-A, UV-B and UV-C radiation on chlorophyll, flavonoids, anthocyanin, proline, membrane permeability, lipid peroxidation and UV-absorbing compound was examined. Results showed that the contents of chlorophyll a, b and carotenoids of pepper leaves were reduced significantly in those plants which were exposed to UV-B and UV-C radiation and compared with control and UV-A treated plants. In contrast, UV-B and UV-C increased (P < 0.05) proline, quercetin, rutin and anthocyanin concentrations in leaves of Capsicum annuum L. Ultraviolet radiation induced oxidative stress in pepper by increasing lipid peroxidation and membrane permeability which indicating that limits of tolerance are much less than damaged caused by UV-radiation. [ABSTRACT FROM AUTHOR]

Two non-metallicolous and metallicolous populations of harmel plants were compared regarding the role of proline, cysteine, reducing sugars, hydrogen peroxide (H 2 O 2 ), glutathione, thiol compounds, organic acids, total free amino acids, and lipid peroxidation in detoxification and tolerance of silver stress (0, 1, 2.5, 5, 10 ppm Ag). The results of the present research state that the effects of Ag were increased total free amino acids, glutathione, organic acids, proline, reducing sugars, thiol compounds, and cysteine, so the accumulation of these compounds was higher in metallicolous populations than non-metallicolous. On the other hand, non-metallicolous populations showed higher content of lipid peroxidation and H 2 O 2 than metallicolous populations under Ag stresses. Also, the accumulation of phytochelatins (PC) was observed with increasing Ag concentration, which shows that compared to glutathione, non-protein thiols have a higher concentration. The number of organic acids (malic acids, fumaric, oxalic, and citric) except acetic acid increased in the leaves of harmel in both populations. According to the results of this research, the harmel metallophilic population has a crucial role in the tolerance and detoxification of Ag stress, so the antioxidant responses of the plant against Ag stress in the non-metallicolous population were lower than the metallicolous population. Based on the above results, it can be concluded that the harmel plant has a detoxification mechanism to deal with high concentrations of Ag., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The objective of this study was to investigate the effects of different concentration (0, 0.1, 0.7, 1.5, 3, 6 and 9 mM) of SA on antioxidant enzymes in Capsicum annuum L. plants. Enzyme activities of peroxidase, polyphenol oxidase, ascorbate peroxidase, catalase and glutathione reductase were measured. The plants were grown in pots vermiculite. Before applying the salicylic acid treatments, plants filled with were irrigated with based nutrient solution (Hoagland solution) for 5 weeks. After 5 weeks, plants were sprayed with different concentrations (0, 0.1, 1.5, 3, 6 and 9 mM) of salicylic acid. Data were analyzed using SPSS software and means were compared by Duncan test. In each experiment 4 replicats were used. Concentrations of 1.5, 3, 6 and 9 mM of SA caused significant increase in polyphenol oxidase and peroxidase enzyme activities in treated leaves. Concentrations of 0.7, 1.5 ad 3 mM of SA decreased in (catalase, ascorbate peroxidase and glutathione reductase) activities, but concentrations of 6 and 9 Mm of SA increased enzyme activities. Different concentrations of salicylic acid had different effects on enzyme activities in Capsicum annuum L.